I have a PSIO. I haven't kept up with it's development lately, so I might be a little outdated.
Their 98% game compatibility is based on the game booting and not about the game being fully functional. Some games work and others are buggy. I think it will eventually get to a very compatible device down the road. If you are okay with the wait and or gamble, then sure get it and enjoy where it excels right now. However your money might be better spent, at this time, on another system.
On a related note, is the Free McBoot for PS2 compatible with PS1 games?