If you are a Gunners fan then this reported move by Vieira to Spurs is effectively a stab in the back. But at age 33, the stab is more like a pinprick.
The key factor is that Vieira himself has given assurances that he would be able to weather the wrath to Hary Redknapp. Everyone knows after nine years of his leaving Spurs for Arsenal, Sol Campbell still suffers at the hands of unforgiving zealots. The saving grace is that unlike Campbell who continued his form even after moving to Arsenal, Vieira is well past that stage. He is desperate for first squad duty which have been rare under Mourinho and is willing to take a massive pay cut to make that happen even if it means going to the Spurs. However it will be difficult to displace Wilson Palacios.
The consensus appears to be that Redknapp is angling more for his leadership qualities rather than actual performance. The other factor is whether Mourinho would let him go on a free transfer. If he does then Viera will become only the 13th player to move between these two clubs.
The Daily Mail has an article on the 13 players who moved between these clubs and concludes what is obvious, Spurs to Arsenal was a better career move.
Vieira was an ardent foe of Spurs and in 17 matches against Tottenham during his 10 years with Arsenal only lost once, scoring five goals.