I have played 3.x since it came out and I ran a 3.5 game for a while. I haven't ran a Pathfinder game though but most of the rules are the same. I was just curious as the overall help that HL offers a GM. I'm currently running my group through an AP so the adventure has most of the stat blocks already figured out..
I have been running a group through Rise of the Runelords (pretty slowly) starting as 3.5, going through PF Beta and now through Pathfinder. I've played D&D since Basic, and didn't get a laptop at the table until two years ago because I was actively against having technology at the table. Here's my take on this question:
Going from 3.5 to Pathfinder just by itself... enough of the rules are different that it makes the conversion a little tricky. There are just so many small changes across the board that you can't rely on almost any 3.5 rule recall. :/ I would suggest to anyone new to Pathfinder to not assume you know the rules for anything no matter how much experience in 3.5 you have. It's always worth a check of the book. Hero Lab "remembers" these differences for you, so that means less book checking for my table.
The Tactical Console is very nice for you if you're the type who puts Initiatives on a white board or index cards. If you just list them on a piece of paper behind your DM screen old school style, then I think it's a steeper curve to learn it. Once I learned the keyboard shortcuts, I found it very smooth and handy to offload a lot of manual work when you get into the entire party and 6+ NPCs.
Where it REALLY shines and makes it worth the trouble of learning is how easy it is to "activate" all those little buff spells and bonuses like charging effects, deadly aim, power attack, bless, inspire courage, a bulls str. potion, etc. All of the ACs, attacks and saves get automatically updated with a click. WAY easier than scribbling down every single +1, +2, -4, +3, +2, +2 every round for your players and monsters... oh yea, this round this guy is sickened... and took 6 pts of con damage so his total HP went down...
Yea. WAY easier to do all of that on the fly with a few clicks and check boxes.
With the addition of the Bestiary & Bestiary 2, you have the options of entering and easily adjusting any NPC / Monster in the game (including the random list in the back of Volume 3) in a matter of minutes. So you decide on the fly that you need a wanding monster while your party is hanging around the woods? Roll a die, import a stock monster from the list, and you're ready for a combat in less than thirty seconds. Less than that if you use the Tac. Con.
If you use a virtual table-top, for either remote players, a digital table or both, there are exports to D20 Pro. This, for me, doubles the benefits of the program because it means the work I do to create anything in Hero Lab effectively duplicates in D20 Pro.