I myself have been using VASSAL for a year or two, primarily to handle the tedious attack run portion of the otherwise intriguing Silent War solitaire game. A well-written module for VASSAL allows you to handle quite a bit of the mundane record keeping with little work, but the critical factor is that someone has to have actually written the code that does that very thing. For example, in the module for A Victory Lost, you can right click on an HQ and turn on the command radius that even takes terrain into account. I had used VASSAL solely as a solitaire aide, never hooking up with an opponent to actually play before.
For our first foray into an online two-player game, we chose the recently re-released SCS game Afrika. The game has many improvements over its predecessor, and even has a pretty elegant supply system that is reminiscent of the much heavier OCS titles without quite so much overhead. The downside is that you have to really think about what you're doing in the game, planning to have supply in a position where it can be used after you've exploited with your units.
We played the Compass scenario, which starts in late 1940 and features the UK forces pushing deep into Libya just prior to Rommel's arrival. There are five "short" scenarios, which double as starting points for anyone who wants to play all the way to the bitter end, and each is only a handful of turns long. Compass has difficult victory conditions (you have to take Benghazi, Tobruk, Bardia, knock out a bunch of boxed Italians in Egyptian territory, and do it in three turns). The game seemed more like a puzzle to me, requiring you to move a fairly small number of units a fairly long distance, and keep them supplied while on the offensive.
Of course, we got about 1.5 turns in, which wasn't bad for a first game. I took a lot of time thinking about how to move, as I was working with an unfamiliar CRT, trying to figure out how best to utilize my supply, protect my supply lines (this didn't work so well - I'd forgotten Chuck had a recon unit under one of the boxes that can slip by enemy ZOCs pretty quickly), and manage to utilize my units in such a way so that I could get the most out of them every turn (exploit-capable units can attack as many as three times in one turn, assuming they overrun in their two movement phases which requires starting out of an EZOC).
All in all, I think this is a very cool game, certainly more approachable for a first title than Stalingrad Pocket (which doesn't have the supply issues, but does have a few other important rules and a lot more counters). On the other hand, we were thinking that perhaps this is a better game to play ftf or via e-mail, seeing as planning your turn can take a while. And it's critical to plan in this case as the British (for example) had a whopping 25 combat units. This is definitely one I'll try to solo in the near future, although given the long map I may need to clear off my two extra tables (currently holding Ambush! and Lock 'n' Load: Band of Heroes).
We haven't decided on a different game, although I'm thinking something involving chit activations like Roads to Leningrad or A Victory Lost. Poor Chuck got stuck waiting for me most of the time, and during his turn I took the opportunity to start trimming the pieces for Death in the Trenches and Totensonntag, two new games I recently picked up.
VASSAL is great for being able to play games with people who otherwise can't get together (Chuck is a good 45 minute drive from my place assuming very light traffic on the I-5 bridge), and it allows you to play games that you may not have the time or space for. On the other hand, it is an imperfect solution: I find I have to really zoom in the board to see the unit designations clearly, if you can see the whole board you're likely to have it zoomed out so much as to miss something, and when it isn't your turn you can't move things around the board or change the display as it affects what your opponent sees (which makes things interesting if you're trying to move some counters around, but the view keeps changing). Also, Afrika had zero bells and whistles, to the point where you couldn't even control-mouse over a stack to see what was in it. It was almost enough to make me want to learn to make my own modules.
As an experiment, I'd say things went pretty well. I don't know that this is the best solution for games that require long periods of time to make your move (if you're playing with both people online, that is - there are e-mail options in that case), but also for a game like Combat Commander where part of the appeal is rapid play - a GUI just can't respond as quickly as having physical components at hand. Still, I think it will be a good way for Chuck and I to get in more wargaming than we usually do, which is always a good thing. Now if only they had a mod for Barbarossa to Berlin...