There would obviously have been a range of opinions.
Hadrian believed that the Empire had grown too quickly under Trajan, giving long borders that were difficult and expensive to defend. The high concentrations of troops required for that defence lead to a dearth within the Empire itself, where they would otherwise increase the security of its denizens.
The policy of using Rome-friendly tribes as buffer states also gained significance at this time, and Hadrian had this at the front of his mind when drawing up the borders. He was clearly a sharp cookie, and there would have been those on the Senate who had the vision to understand and agree with his actions.
Arguably, this was a continuation of a policy that had its roots as early as Augustus, but largely it is felt that, up to Hadrian, the Romans felt their empire would keep on expanding forever, and it was the duty of every Roman general to keep that outward expansion pressure going. There would have been those on the senate that saw the frontiers as an end to the glory days, and consequently be mad as hell about it. Not only because of the glory, but because wealth would now have to be earned, rather than pinched off the neighbours.
Those who fell into the latter camp, would be further split into two. Those who kept their mouth shut about it, and those who risked annoying the new Emperor by vocalising their opinions. Although Hadrian was adopted and nominated by Trajan, he was not a shoe-in for Emperor and had to work hard to gain popularity (he publically burned all the tax records). There were those who had opposed his claim to the purple, and who no doubt regretted it when they had the error of their ways brutally pointed out to them. Some would have to tread very carefully in considering what they said in the Senate.
As to Hadrian's Wall itself rather than just the drawing up of the Limes, it underwent a number of changes during the latter part of construction, or very soon after. These are principally in connection with the practicality of a wall as a defensive frontier, as opposed to a traditional defensive wall around a fort or city. It is not beyond the realms of possibility that Hadrian was closely involved in the design of the wall, modelling it on fort/city walls. He famously did not take kindly to having his architectural skills critcised, and so you can see a scenario where, as soon as he left, the military leaders on the ground said, "OK lads, he's gone!", and made the changes.