Ok...I was looking at this build and thought "wow". So, I decided to come up with my own version of it. After looking the build over and looking at what subbies I had available on my second account, I decided on Undying. Here's the resulting build plan:
Race: Elf
Subrace: Undying
Stats:
8/20/10/16/8/8 (Elf)
10/22/14/18/10/10 (Undying)
Feats:
(Dodge, Luck of Heroes, Iron Will, Lightning Reflexes, Great Fortitude)
1: Point Blank shot
3: Weapon Focus: Light crossbow
6: Rapid Reload
9: Blind Fight
10*: Improved Evasion
12: Improved Critical: Light crossbow
13*: Opportunist
15: Toughness
16*: Crippling Strike
18: Shield Proficiency**
19*: Defensive Roll
21: Great-Dex 1
24: Great Dex 2
24*: Epic Skill Focus: Search
27: Epic Weapon Focus: Light Crossbow
28*: Epic Dodge
30: Epic Prowess
32*: Epic Skill Focus: Disable Trap
33: Armor Skin
36: Self Conceal 1
36*: Self Conceal 2
39: Self Conceal 3
40*: Self Conceal 4
42: LWF: Light Crossbow
45: L-Fort
48: L-Will
51: Self Conceal 5
54: Skill Mastery
57: Improved Sneak Attack
60: Improved Sneak Attack
** There are several options for the feat at Level 18:
--Shield Proficiency (What I took, and recommended if you don't have an item that grants this feat) - Allows you to switch to a sling and shield combo in case you need the extra AC in order to tank something.
--Weapon Finesse (recommended if you have an item that grants shield prof) - Allows you to switch to a melee weapon (and shield). Useful when you need to tank something, or when your bolts aren't working.
--Skill Focus: Disable Trap - An interesting option in that it allows you to drop ESF: Dis. Trap in favor of another level of improved sneak (if you don't have a sneak pandect), or L-Luck (you should be able to take Skill Mastery at 24 and L-Luck at 54), but requires more +DT equipment and something with +10 or more int on it, and you can't use a melee weapon (or a shield unless you have some way of getting shield prof)
Ending Stats:
10/48/14/18/10/10 nekkid
22/60/26/30/22/22 In full battle gear
both of these assume the extra +4dex in LLs from being a rogue, no arti, and no demi iterations.
Notes on this version:
Saves should be 59/75/57, according to my calculations.
If you don't have a sneak pandect and/or want better saves (these are fine for me), you can swap the 2 great dexes out for L-Luck and Imp. Sneak attack. Note that the Dim Mak robes give Epic Will, so you can push will over 60 without any changes if you have a set, and getting your first demi will put fort at 60.
I'm holding off on the improved sneak feats so that I can eat the sneak pandect I have first and wind up more sneak damage than I would otherwise. If you don't have a sneak pandect and want to take them earlier, you can.
As for skills, with 18 base int, undying, and the bonus from being a pure rogue, you should have no lack of skillpoints.

In any case, comments on this build would be very welcome.

--Arek
*Updated 2/25/2009 to fix a problem with feats (thanks, t1k), and list some alternatives to shield proficiency.
*Updated again to switch Weapon Focus and Point Blank Shot around (thanks, Johann).