If all you're going to do is simple PDA stuff, then you should be ok. The only problem you're going to bump into is the RAM limitation. You've only got 32MB of RAM in that device.
Pocket PC Techs can upgrade that device for a reasonable fee. (about as much as you'd spend on a decent SD card...if the 3600 could actually USE an SD card without a CF/ PC Card Sleeve and some sort of adapter...)
You can see the details here:
http://www.pocketpctechs.com/i3600up.asp
Please also remember that you will need sleeves for any sort of expansion. CF and PC Cards can only be used with sleeves. You can pick many of those up on eBay for a fraction of their original cost.
Let me know if you need any further help!
Kind Regards,
Christopher Spera