I use the SMC 2632W in a PC card sleeve on my ipaq. Since I already had the SMC for use with my laptop, it made more sense for me to pick up the PC card sleeve for $100 than to spend much more than that on a wireless CF card. Also, the PC card sleeve has a second battery to power the PC card, and will allow for more potential device support than the stock CF sleeve. My only complaint with my setup is that the SMC card seems to have less range in the ipaq than it does in my laptop. I'm not sure if it's a power output issue, or if it's because I had to use drivers from another manufacturer since SMC does not provide any for WinCE.
Since it seems that you don't already have a wireless PC card, it probably would be a bit cheaper to just buy a CF wireless card, and it would end up being a more compact solution since the PC card sleeve is about 1/3" deeper. On the other hand, if you need the extra battery life, want more expandability, and don't mind the extra size, the PC card + sleeve may be a good option.
Here is a list of currently supported PC cards under WinCE. Most of the common consumer ones (Linksys, D-link, SMC) use the same chipset so they can use the driver provided by Compaq. There are also a few that do not yet have drivers, so if you go the PC card route, avoid those. There is a link at the bottom of the page to CF cards that will work, but I suspect that pretty much any one will do since they are designed for Palm / Pocket type PC's running CE.
~bex0rs