On an impulse we decided to drive from Bangalore to Chennai.
There are two options : one via Hoskote and Kolar, and the other via Hosur, Krishnagiri, Ambur and Vellore, and both these routes merge at Ranipet, after which you cross Kanchipuram and Sriperumbudur before reaching Chennai. After asking many travellers, we chose Hosur, and man, are we are grateful to those who suggested this. The highway is awesome, at least upto Ranipet, and even my tired, old WagonR was clocking 130+ speeds without a murmur. We took around 7 hours to reach Chennai.
One more tip, please leave as early as possible to beat both the rush of cars / trucks / buses, and also to minimize the travel time in hot conditions. We left Bangalore at 4.30 AM, and reached our hotel at Chennai by 11.30 AM. Breakfast suggestions : Any of A2B, Krishna Sagar, Dhaba Express, or even McDonald's near Krishnagiri. If you leave early enough, then you can have lunch at Chennai, but if you are not an early riser, then lunch options are Star Briyani at Ambur, and Saravana Bhavan (veg) or The Vellore Kitchen at Vellore.
One word of caution for the Hosur route : there are as many as 7 toll booths in this 350 odd km stretch, and the total amount (one way) comes to around Rs. 400, but when you drive on the road, you will feel that every rupee you have paid is worth it.