Of course you can boot!
It will be fast enough. The problem is the limited read/write cycles that the CF card have. It's not recommended to use the CF as a boot disk cause it's constantly working and it will stop running after some months period. It's the best for backup reasons and transfering file via mounting the CF to a PC using UAE.
Another thing I discovered is that if you cut the power while the CF is running you experience problems on the disk 90%. After that, only format is an option.
I hope I helped a bit.
