I wish him well Mifune but as you say, Senna 'B' did not - and is very unlikely to - set the world alight. Being 0.3 seconds adrift of Button's time is no mean feat, especially if the time was set under near identical conditions. But of course even if that was the case, lap time is not the whole story (I have no idea whether it was incidentally, so perhaps you could advise me?).
An F1 test involves giving feedback to engineers, which is assessed for accuracy / clarity / usefulness / direction etc. From what I've heard, Senna was not stunningly impressive in this department. Button on the other hand, is probably the best in the business, being at least on a par with Alonso and better than Vettel who still lacks a bit of experience. (Hamilton is a complete oddity here; a bit like a modern day Jim Clark: his technical feedback is very personalised and sometimes ambiguous, due to his ability to drive around 'problems'. Incidentally, this is one area where he and the team are definitely benefiting from Button's excellent technical ability).
Back to Senna, you mention that he "has not had a proper chance yet…" but I base my assessment not on the car he was driving but the way he drove it. He made lots of mistakes and was not consistent with his lap times or even the positioning of the car from lap to lap, by which I mean he did not look especially expert at setting up his car from corner to corner (from a purely driving point of view). In F1, this should be a 'given' but Senna 'B' sometimes looked like an enthusiastic semi-pro, i.e. rather 'scruffy'. I honestly believe that the only reason his career resulted in a Grand Prix drive was because of his name. As far as I am aware, throughout his career he has been given the very best opportunity from helpful and hopeful sponsors; and on paper at least, this is a significant advantage over his rivals.
P.S. I'm not a fan (or critic) of any driver in particular, although I hope I appreciate some of the differences between them. But ultimately I still have an opinion which can of course be as wrong as anyone's!

Good luck to Bruno - along with the others I've perhaps been rather dismissive of recently: Grosjean; Karthikeyan; Hulkenberg; Rosberg maybe? Oh, and some other German…
An F1 test involves giving feedback to engineers, which is assessed for accuracy / clarity / usefulness / direction etc. From what I've heard, Senna was not stunningly impressive in this department. Button on the other hand, is probably the best in the business, being at least on a par with Alonso and better than Vettel who still lacks a bit of experience. (Hamilton is a complete oddity here; a bit like a modern day Jim Clark: his technical feedback is very personalised and sometimes ambiguous, due to his ability to drive around 'problems'. Incidentally, this is one area where he and the team are definitely benefiting from Button's excellent technical ability).
Back to Senna, you mention that he "has not had a proper chance yet…" but I base my assessment not on the car he was driving but the way he drove it. He made lots of mistakes and was not consistent with his lap times or even the positioning of the car from lap to lap, by which I mean he did not look especially expert at setting up his car from corner to corner (from a purely driving point of view). In F1, this should be a 'given' but Senna 'B' sometimes looked like an enthusiastic semi-pro, i.e. rather 'scruffy'. I honestly believe that the only reason his career resulted in a Grand Prix drive was because of his name. As far as I am aware, throughout his career he has been given the very best opportunity from helpful and hopeful sponsors; and on paper at least, this is a significant advantage over his rivals.
P.S. I'm not a fan (or critic) of any driver in particular, although I hope I appreciate some of the differences between them. But ultimately I still have an opinion which can of course be as wrong as anyone's!

Good luck to Bruno - along with the others I've perhaps been rather dismissive of recently: Grosjean; Karthikeyan; Hulkenberg; Rosberg maybe? Oh, and some other German…
