^ Ditto
If you believe you're clueless now it will only become worse with the current version of 5. Consider this... if you have an issue with 4.2.1 you could post for assistance OR more than likely search for an answer and find it pretty quick but doing the same for vB5 issues might make you spin wheels. The reason being many are still having issues with vBulletin 5, heck I work for a major host and can tell you their clients have issues with vB5 so I dare say I know from experience the headaches many of these owners share.
Will it improve over time? Sure

but until it does and I see less people having headaches dealing with it I'm not going to come in here and lie to you, instead I'll do as I just did and try to sincerely warn you ahead of time that you will have less stress and headaches running 4.2.1/4.2.2 as opposed to 5.x

.