If you live in the Dallas area, you already know this topic only too well.
If you are planning on passing through Dallas on your way to a warmer location, or for what ever reason . . . plan your route to
AVOID I-635 North (otherwise known as LBJ Freeway). I-635 North is a common transit to go from US 75 to I-35E.
There is a 5 year construction plan (only recently started) which will widen I-635, sink a tollway/HOV lane at a lower level in the middle of the east/west lanes, elevate frontage roads, etc. All this in the name of progress!
I am posting this at this time only because we just got a message here at work from the Dallas Emergency Response Team. On this LONG email, there are 25 specific items (such as lane closures until 2013, bridge closures until 2014, etc.) detailing the nightmare that will represent I-635 for the coming years.
Some of the alternatives are not that great either. There is heavy construction north of downtown Dallas on Woodall Rogers Freeway for the next couple of years. ("They" are building a park above the Freeway!) I-30 south of downtown is OK, but it is quite a run through "The Canyon".
TX 121 from McKinney to Lewisville is good, but it is now the Sam Houston Tollway. The George H. W. Bush Tollway is another alternative from Plano to Carrollton. On these tollways, you just keep driving and get a picture of your license tag taken, and the North Texas Tollway Authority will send you a bill. Pay or a larger billable amount will soon show up.
If you do take TX 121 west, be aware that 121 and TX 114 are under heavy construction north of the DFW Airport (south of Bass Pro). I will drive an extra 20 miles to personally avoid this area!
Probably the best alternatives are US 380 from McKinney to Denton. On the east side of Denton, take Loop 288. If you need to go to Camping World, take Loop 288 North (which is north of the I-35 split). If you want to continue south to warmer regions, take Loop 288 South. Where Loop 288 intersects I-35E, a left turn is permissible out of both lanes under I-35E - just watch out for the "lane crossers". Otherwise, the southern alternative is I-20 across south Dallas to Arlington and Fort Worth.
For total piece of mind and low stress, I would avoid the whole Dallas-Fort Worth area and also the whole Houston metroplex!
Ron