I currently use my laptop with an Excel spreadsheet I wrote for my char sheet.
Key aspects:
- every skill, feat and spell is hyperlinked to d20srg.org's specific URL so I can pop-up the rules
- the experience tab logs my XP, totalling it up for me (thus tellimg me I leveled, and it stores the results of each new hit die
I use 1 tab per topic (general, skills, feats, spells, equipment, experience, combat)
The combat tab shows my total attack bonus for each weapon I have readied, and my current AC
It also has the ability to add/subtract HP as I take damage. This is crucial for a charsheet, the ability to click a button, fill in how much damage I took, and have it do the subtraction easily.
I don't need a dice roller, certainly not one that puts a lot of art into it. If I did have one, I'd make it just roll attack rolls and damage in a simple format so I can read the results to my GM.