Ran WB 3.0 with 3.1 ROM's for awhile. No issues to report, actually the A500 plus felt quicker to me.
Upgraded to WB 3.1 which felt slower. Anyway works fine.
Also to note had more chip RAM available under 3.0.
Although on the A1200 with custom 3.9 roms and OS 3.9 I can achieve more chip than on the A500 plus.