Personally, I'd have gone more heavily into warblade, something like Rogue4/Swordsage4/Warblade12, or thereabouts. The sneak attack dice are nice, for certain, but there's all sorts of other interesting strikes you can get from higher warblade levels. The tiger claw chain is really nice, especially if you get the mongooses (extra attacks) and the tiger's pounce (level 5, IIRC) maneuver. Combining lots of attacks with stormguard warrior is also killer, and warblade has a full BAB.
Your plan is pretty good, though, sacrificing some BAB and maneuvers for SA dice. It's also better at skills, the Warblade version has far fewer useful skills, requiring that feat whose name slips my mind which fiddles your class skills.
Personally, while Swashbuckler is nice for weapon finesse, it's not awesome for int-to-damage. Warblade gets int to damage anyway, and it's a precision thing, not worth dumping two more levels into it, when you could have more warblade maneuvers. But that's just my opinion. Overall, I still think your build is solid.
Stormguard Warrior looks nice, but generally I find that with spellcasters in the party, there's no guarantee that any given opponent will last long enough for me to spend a whole round tapping them ineffectually. Better to treat each round like it's my last chance to do something useful.
Anyway, I don't really want to be the tank, as I played that role in the last game and I'm a bit bored of it now. I set out this time to make a capable Rogue, because I've never played one in 3.5 and have always wanted to. Also, there's another player at the table who doesn't believe Rogues can be useful in combat, saying it's too hard to set up a full-round of sneak attacks. I really want to prove him wrong, which is why I'm so torn over Sudden Leap.
Umm, that's a weird sentence. Let me put it together backwards. The feat can be activated once per day. It lasts one minute (10 rounds). During that time, you can move your base move as a swift action. That's usually enough to reposition and still take full-round attacks.
Better yet, if you have a cleric level, you can trade the travel domain for the travel devotion feat, and permanently sacrifice turn attempts for additional uses of that feat per day. There was a thread about dipping 1 level in cloistered cleric - it's a great dip for just about everybody. Knowledge devotion, Travel devotion 3 or 4 times per day, depending on your Cha, and some other useful domain (Magic is good).
You can also load up on items from the MIC. The chronocharm of the horizon walker lets you move half your move as a swift action 1/day, the anklet of translocation gives you a 10' swift action teleport 2/day (required for anyone who doesn't have any other dimension hop ability, for escaping grapples and suchlike). The belt of battle gives you extra move actions, or in a pinch an extra full-round action each day.