Conversion notes
I took your advice and checked on the converted creatures. The party is currently tackling the area in and around "The Lea" which required updated creature stats for Verbeeg Giant-kin. The updates seem to be in line with what a Verbeeg should have for power and such in 3rd edition. Considering they are basically a step up from ogres, this seems to be about right.
The one thing I'm a bit confused by is the fact that they only qualify for CR3 monsters. I guess it makes some sense since Ogres are only consider CR2. However, the damage they can dish out along with their relatively high AC makes them very challenging for that level. With AC19, +9 with their melee attacks and damage of 2d6+9, that makes them extremely powerful opponents. The party of 6 characters averaging about 6th level right now faced 2 adult Verbeegs and 1 young (treated as a bugbear). The 2 adult verbeegs were quite close to killing 2 of the characters. No critical hits or ambushes, just a straight up fight in which the party had a solid upper hand to start things with. +9 on attacks basically turns them into a 50% or better chance of dealing damage to party members since the best AC in the group is 20. Discounting the young Verbeeg in this encounter which was not a factor, the 2 "CR3" Verbeeg would be about an EL4 encounter which should be quite easy for a 6th level party. However, it taxed them pretty heavily with the cleric pitching all of his 3rd level spells and a few 2nd level ones to keep the fighters alive. And the wizard burned a few of his better spells as well. Seems like a CR3 rating here doesn't match what the playtesting revealed in this case.
Otherwise, looking ahead, I don't see any major problems besides the possible lethalness of some of the situations. Giants in 3E are "a lot" tougher than their 2E versions. At 5th level, this party was having a cake-walk against Hill giants, but now they almost die to stuff like that. Party levels likely need to be a bit higher than they did in the past. A 5th to 6th level party facing a handful of giants had a fighting chance. Now it's not as easy. So just be careful not to go overboard unless you intend to make it really hard for your party.