Westpac Altitude transfer to Velocity doesn't look too attractive to me except for flights. Check out the maths & note conversion given is 50% plus 15% bonus, so it nets out at 575 Velocity points for every 1,000 Altitude points.
Example 1 $100 Myer Gift Card. Velocity costs 13,500 points and I would need to convert 23,480 Altitude points to gain this number of points. Altitude offers this reward for 16,950 points, so conversion makes you 40% worse off.
Example 2 iPod 16GB. Velocity costs 25,000 points and I would need to convert 42,500 Altitude points to gain this number of points. Altitude offers this reward for 40,575 points, so conversion makes you 5% worse off.
Example 3 GoPro Hero 3. Velocity costs 63,000 points and I would need to convert 107,100 Altitude points to gain this number of points. Altitude offers this reward for 68,100 points, so conversion makes you 58% worse off.
Example 4 Reward Flight BNE/MEL. Velocity costs 13,000 points and I would need to convert 22,100 Altitude points to gain this number of points. Altitude offers this reward (same flight) for 36,750 plus tax points, so conversion makes you 40% better off.
You would need to do more analysis to check out my theory but unless you use your points for flight you are better off not converting your points.